Rc, is this a small propane torch like a plumber might use to sweat joints or a large propane torch like a weed burner?
Small one doesn’t put out enough BTU’s to heat a spike. The large one will work but you need to build a surround to trap the heat in rather than let it all dissapate. You can do this with a bunch of firebricks stacked around the piece with a hole to insert the torch and another one to put in take out the spike—watch out as hot gasses will exit that hole as well. Another method is to line a piece of nongalvanized steel with kaowool and stick the blower in that. Or you could just dig a hole in the ground outside and get some lump charcoal and a blowdryer and have a forge… Acetylene will be an expensive way to heat metal. google propane forge and you will find a lot of plans out there to build the forge and make burners from common plumbing parts.
